1. Technical Field
The present invention relates to an image processor, a method for processing an image and a computer readable medium.
2. Related Art
Conventionally, when reading an image on one side of an original sheet which has images on both sides thereof or an image of an original sheet on which one or more other original sheets are stacked, there has been occurring a so-called back-side or non-target image reading in which the image on the back side of the original sheet or the image on the one other original sheet stacked on the original sheet is read together with the image on the target side of the original sheet through the same original sheet. In addition, when taking a photo of a subject through a sheet of glass with a digital camera, in some cases, there occurs a so-called non-target image pickup where a scene which has nothing to do with the subject is reflected on the surface of the glass and is eventually picked up together with the target subject. As a result, in either of the cases, images are obtained in which the blurred image which is undesirably read or picked up is superimposed on the desired target image. In the following description, the state in which the blurred undesirably read or picked up image is superimposed on the desired target image will be described as a non-target image superimposition.
As one of techniques which eliminate the non-target image superimposition, a technique is known in which images on both sides of an original sheet are read together, so that the image read from the back side of the original sheet is eliminated by referring to the images on both the sides of the original sheet. In addition, as a method for eliminating the non-target image superimposition from an original sheet which has an image only on one side thereof, there has conventionally been adopted a method in which a so-called background removing process is implemented. The background removing process is such that a gradation correction is performed on the read image according to a certain fixed value or detected background level.